Bob

A highly maneuverable flyer. He’ll try to stay slightly above the player by flying upwards whenever he shoots. If the player is far below him, however, he won’t fly up, choosing instead to go lower, down to the player’s level. On Nightmare skill, the bobbot moves slightly faster when firing.

Necros says
Because of their maneuverability, fights with these guys may last longer than your typical quake monster fight would, and because of their small size, the SSG is mostly a waste against them. Keep this in mind that players will want to use nails the most to take them out, or if there is one bob alone, a normal shotgun should do.

Kell says
Aiming at bob is the hardest part of combat here, with dodging his laser volley coming second. Nail weapons feel the most natural against bobbots, but the RL makes for a good challenge because it only takes a couple of hits but those hits may take a bit of effort to score. As with other flying monsters, distance makes the GL and LG less effective. The PG will burn them down very fast, but if the player wields it in later areas of a map several bobbots can be used without overwhelming the combat.
Try to give bob a bit of space to maneuver. The simplest way to achieve this is to raise the ceiling height of a room.